Process of stripping tin from tinned iron and recovering the metals.



ploy persulfate of iron to dissolve the tin, and

thrown down at the same time.

UNITED STATES PATENT OFFICE.

HENRY WILLIAM HEMINGWAY, OF LONDON, ENGLAND.

PROCESS OF STRIPPlNG TIN FROM 'TINNED IRON AND RECOVERING THE METALS.

SPECIFICATION forming part of Letters Patent No. 663,024, dated December4, 1900.

Application filed May 7, 1900. Serial No. 15,820. (No specimens.)

1'0 all whom, it may concern:

Be it known that I, HENRY WILLIAM HEM- INGWAY, a subject of the Queen ofGreat Britain and Ireland, residing at Albyns, Forest road,\Valthanstow, London, in the county of Essex, England, have invented anew and useful Improved Process for Use in Stripping the Tin from TinnedIron and Recovering the Respective Metals, of which the following is aspecification.

This invention relates to an improved process for stripping the tin fromtinned-iron clippings and similar waste with a view to the recovery ofthe tin as also of the stripped iron or steel.

In carrying out my improved process I emthus to remove it from the iron,and I continue to add further quantities of the tinnediron' clippingsuntil thepersulfate has been converted into protosulfate. Upon thisstage being reached, the tin deposits itself as an oxid, some insolublepersulfate of iron being The precipitate may then be dried and the tinseparated by smelting or by chemical means from the ferric salts.

A solution of persulfate of iron is known as a powerful oxidizing agent;but the essential feature of my invention consists in its use as asolvent of tin, the continued application of tinned iron or even iron tosuch a solution having the effect of exhausting the oxygen, convertingthe persulfate into a protosulfate, and throwing down the tin as aprecipitate.

The following formula illustrates the reactions which occur:

It may, however, be observed that the proportion which may happen toprevail between the persulfate of iron and the metal, as also theproportion of the one metal to the other, will entail modifications inthe terms of the equation. Difference in the temperature at which theoperation is conducted will also occasion a larger or smaller quantityof the persulfate of iron to be precipitated, the formula undergoingcorresponding variations.

Should it be desired to diminish the tendency of the persulfate of ironto precipitate with the oxid of tin, sulfuric acid may be added to thesolution of persulfate of iron. Under such circumstances the persulfateof iron, when reduced to protosulfate, ceases to act on the tin, andstripped or other available iron may be added to take up the acid, andthus allow the oxid of tin to precipitate. A similar result may beaccomplished by adding sulfid of iron to the tin-charged solution ofsulfate of iron. In this case a reaction takes place, the added irongoing into solution, while the tin is precipitated as sulfid.

What I claim'as my invention, and desire to secure by Letters Patent, is

The herein-described process for stripping tin from tinned iron andrecovering the tin, consisting in treating the tinned iron with asolution of persulfate of iron, continuing to add iron until thepersulfate is converted into protosulfate and the tin thrown down as aprecipitate, collecting the latter and recovering the tin therefrom.

HENRY WILLIAM HEMINGWAY.

Witnesses:

F. F. PALMER, W. H. DORMER.

